A Visible-Light-Driven Molecular Motor Based on Pyrene

The aromatic core of an overcrowded alkene-based molecular motor is extended with the goal of inducing isomerization with visible light instead of harmful UV light. In our design, the common naphthalene moiety in the upper half of the motor is changed to pyrene. The photochemical and thermal isomerization processes are studied in detail using DFT calculations as well as NMR and UV/VIS spectroscopy. Our studies confirm that extension of the pi-system of the upper half successfully leads to a shift of the excitation wavelength into the visible region, while retaining proper rotary function.